Internal combustion engines require a source of combustion air. A typical source for combustion air is outside air which commonly includes particulate contaminants. An air cleaner including an air filter element is normally provided to capture these particulate contaminants before combustion air is delivered to the vehicle engine. When operated in colder climates where heavy or blowing snow is common, snow may be drawn into the air cleaner and lead to eventual blockage of the air filter element, thereby cutting off the supply of combustion air and leading to poor engine performance.
In the prior art, air cleaners are known that include a secondary air inlet having a movable damper or power operated valve operable to open a secondary air supply to the air cleaner when the primary air supply becomes obstructed by snow. One example is U.S. Pat. No. 4,969,939 which discloses an air cleaner equipped with a slideable valve including mechanical linkage extending into the operator cabin and operable by a vehicle operator to admit secondary air into the air cleaner in the event the normal air inlet becomes blocked by snow.
U.S. Pat. No. 6,395,048 discloses an air cleaner having an annular door with an open window that is rotatable between a first and a second position. In the first position outside air is admitted to the air cleaner. In the second position warmer under the hood air is provided to the air cleaner and the normal outside air inlet is blocked. The door is rotated by a mechanical actuator.
As can be understood from the above, many varieties of air cleaners equipped for secondary air induction are known. As can be seen from the prior art, air cleaners equipped for secondary air induction have a number of moving parts, are more complex and are therefore more costly that similar air cleaners lacking secondary air adaptations.
As can be appreciated, at the time of manufacture the ultimate service condition of the vehicles are not typically known and therefore the proper air cleaner type and configuration can not be predetermined. Only a portion of manufactured vehicles find service in northern frigid environments in which heavy snows and air cleaner snow pack conditions can be expected. Providing all manufactured vehicles with more costly secondary air equipped air cleaners is unnecessary and undesirable. Also as can be understood, known air cleaners are either secondary air equipped or are not so equipped. Known air cleaners are not configured for end user conversion to add secondary air induction to an air cleaner after market or in the field.